This invention relates to pin-tumbler locks that are pick-resistant, and more particularly to pin-tumbler locks of both the concentric cylinder type and the tandem disk type that include defensive means to resist picking.
Pin-tumbler locks of the concentric cylinder type of the prior art are described and shown in the early patents of Linus Yale (U.S. Pat. No. 31,278 and U.S. Pat. No. 48,476). A typical pin-tumbler, key-operated, cylinder lock is opened by a key that raises each pin stack within the lock until the bottom of the top pin of each stack lines up with the common circumferential surfaces of an inner cylinder and an outer housing bore. When all pin stacks are thus aligned, the key can rotate the inner cylinder and thereby operate any number of mechanisms attached to the far end of that cylinder or cammed by it.
Pin-tumbler locks of the tandem disk type of the prior art are described and shown in the patents of Frank Scherbing (U.S. Pat. No. 4,621,510) and Morris Falk (U.S. Pat. No. 3,961,507). A typical tandem disk pin-tumbler lock (often known as a tubular key lock) is one wherein a disk plate rotates one end flat surface against a stationary flat surface internal to the housing of the lock, and bores aligned through both plates contain pin stacks and springs. Like the concentric cylinder type, the moving plate can rotate only if the lock's key pushes on all pin stacks in a proper combination to line up the bottoms of all top pins with the interface plane between the movable plate and the housing's immovable mating surface. A concentric shaft extending as a part of the movable plate through the back of the housing is often used as a means to drive cams or mechanisms to unlock the device wherein the lock is assembled.
Any currently manufactured pin tumbler key-operated lock can be picked or manipulated open or otherwise compromised by (1) the application of a rotating or probing force upon its locking cylinder or locking disk while simultaneously (2) pushing, positioning, or separating the locking pin stack elements with appropriate tools.
Various pin-tumbler locks exist that use a second rotating member, whether a concentric cylinder or a tandem disk, but none has been created that cannot be picked, manipulated, or impressioned to an unlocked state without the use of its provided key.
Prior art structure, wherein a pin-tumbler lock utilizes a second cylinder concentric to a first for the purpose of making the lock pick-resistant but without using a second stage of unlocking is shown by Barker in U.S. Pat. No. 1,417,132.
Prior art structure of an improved pin-tumbler lock that uses a second tandem disk for the purpose of simple resetting of the lock for several different key codes is set forth by Falk in U.S. Pat. No. 3,961,507.
Prior art structure of a pin-tumbler lock that uses a second cylinder concentric to a first for the purpose of greater security in master-keying is set forth by O'Keefe in U.S. Pat. No. 414,720.
Prior art structure of a pin-tumbler lock that uses a second cylinder concentric to a first for the purpose of convenient removal of the lock's core from its housing by using a second key is set forth by Best in U.S. Pat. No. 1,384,022.
As such it may be appreciated that there continues to be a need to improve the security of pin-tumbler locks from picking, manipulation, and impressioning as set forth by the instant invention which addresses both the problems of effectiveness of security and ease of construction.